<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var lengthOfLastWord = function(s) {
    let index = s.length - 1;
    while (s[index] === ' ') {
        index--;
    }
    let wordLength = 0;
    while (index >= 0 && s[index] !== ' ') {
        wordLength++;
        index--;
    }
    return wordLength;
};
console.log(lengthOfLastWord("Hello World"));
  </script>
</body>
</html>